Seals are used in order to be able to control whether a closure has been opened or a connection has been disconnected. Hence, for example, seals are affixed at Customs in order to ensure, for example, that sea-freight containers contain precisely those goods listed on the corresponding Customs documents. For this purpose, Customs uses wire loops, the ends of which are connected to a seal. The seal also enables checking as to whether the seal has been replaced by a new seal. In the field of medicine, for example, seals are placed on sterilization containers in order to be able to control whether such a sterilization container has already been opened following sterilization and to ensure that the instruments in the container are still sterile without fail. Various types of seal are provided for this purpose.
One very simple type of seal for sterilization containers works according to the cable tie principle, that is, a plastic loop is fed through both an eyelet on the container lid and an eyelet on the container tub and is then sealed. This type of seal is locked by its one end being provided with one or more indentations, the edges of which, pointing towards the proximal end of the loop, are tapered, while the edges pointing towards the distal end are set at a steep angle. A head with a through-hole is arranged at the other end of the loop, into which a flexible detent lug protrudes. The proximal end of the loop is introduced into the through-hole so that the detent lug snaps into the indentation. Due to the steep angle of the one edge of the indentation and the corresponding shape of the detent lug, it can be ensured that the proximal end of the loop can be easily inserted into the through-hole, while pulling on the loop does not result in the proximal end being released from the through-hole. Labelling areas or similar can also be provided on such a loop. This type of seal is intended only to be able to be opened by being destroyed i.e. by the loop being cut through at one location.
The problem with this type of seal is that it is not protected against intentional tampering. That is to say, the head of the seal can be drawn out using a thin object, and the flexible detent lug can be deformed out of the indentation, against the spring effect, at the proximal end of the seal and thus the seal can be opened without destroying it. It can even be used again afterwards and so it is no longer able to fulfil its function of securing the original condition.
As well, there is also the problem in the clinical area that a correctly opened seal, that is a destroyed seal, only loosely hangs on the two eyelets of the container and falls off easily if the lid is removed from the container tub. Since the floor of an operating theatre is considered not to be sterile, a seal which has fallen cannot simply be picked up. Since several containers are often used, frequently, as a result, several seals fall to the floor and impair the safe footing and movement and hence the concentration of the personnel.
Another safeguarding system for sterilization containers consists of a flexible card which is inserted sideways into a slot so that its free end rests in front of the locking tab. The inserted end of the card also has special recesses or holes which engage corresponding projections in the slot so that, at least with a sealed container, the card cannot be easily removed from the slot and inserted again. If the locking tab is now opened, the card bends back and then catches behind the locking tab, in its original position. If the locking tab is now closed again, the card is behind the locking tab and is no longer in front of it, and so it is indicated that the container has already been opened. The mechanism which requires exchanging the card for a subsequent sterilization process, however, is relatively complicated and hence expensive, is prone to failure and has a negative effect on the sterilization result. Moreover, this security device is also not tamper-proof. The card can be bent forwards prior tore-sealing the locking tab using a thin object so that it is then positioned in front of the locking tab again.
Another major problem with the seals and security mechanisms known to date is that it often cannot be discerned at first glance whether or not these have already been circumvented or vandalized. For example, with a seal in the form of a loop, a vandalized seal can be re-threaded into the eyelets on the container and an unwary user will not necessarily notice that the eyelet has already been vandalized and hence circumvented.